What are Phosphates?

Copyright ReefNation 2012

Phosphates (po4) are organic molecules found in most ecosystems around the world. They are essential for many life processes and thus must be present for life to exist. In the reef aquarium, the main challenge is keeping these phosphates present, but not allowing their concentration to rise above a certain threshold which can be harmful to corals.  It is important to know where Phosphates come from in the reef aquarium, how to detect if they are present, and ultimately what you should do about removing them.

Where do Phosphates come from?

Phosphates in the reef aquarium can come from many sources including fish food, live rock, and even the salt water that is mixed for water changes. Depending on water parameters, specifically pH, phosphates can actually be released from the dissolution of calcium based sediments where they have been sequestered. This underlies again the importance of keeping your reef aquarium as stable an environment as possible in so far as the calcium, alkalinity, and pH parameters are concerned.


Testing for Phosphates in our Reef Tanks

Testing for Phosphates has been a challenge in years past due to the inaccuracy of most testing kits.   Above levels of .1 ppm, some stony corals will suffer both a significant slow down of calcification as well as potentially

Copyright Hanna Instruments 2012

experience a bleaching of their tissues.  It should be noted that some corals such as soft corals and some LPS corals can actually thrive with a higher level around .25ppm, but this is the exception rather than something to aim for.  The levels that are needed to maintain a healthy reef tank tended to be so low that most test kits just simply could not detect them. In the last year or two however, a few electronic test kits such as the Hanna Checker series (phosphate) have made getting an accurate handle on phosphates not only possible, but also fairly cost effective. Hanna has also shed some electronic light on the accurate testing of Alkalinity and Calcium recently which also made getting a handle on these parameters far easier and more accurate.    Since phosphate levels on most reefs of the world are about .05, this is where we aim to keep our tanks here at ReefNation.

Phosphate Removal

While a certain amount of phostphate is necessary for the biological functioning of corals, it is very easy to have too many phosphates in the reef aquarium.  There are various ways to remove phosphate from the reef aquarium. Some of the most popular ways to export phosphate are through water changes,  with a media reactor filled with a phosphate removing GFO, as well as through sequestration in a natural media such as the macro algae Chaetomorpha or the addition of Kalkwasser.


Copyright Bulk Reef Supply 2012

One of the more simple ways to prevent phosphates from getting into the reef aquarium in the first place is to make sure you rinse your fish food before placing it in the tank. The water portion of this food is notorious for containing high levels of phosphate and this method is a simple way to remove that.  As long as these lower phosphate levels are maintained in the coral reef aquarium where all other impotant parameters are maintained correctly, corals will thrive and exhibit normal growth and coloration.

What have you done to keep phosphates in check on your reef tank?